Shoulder prothesis

ABSTRACT

The present teachings are directed to a modular shoulder prosthesis having an adjustable radial offset and/or angular inclination provided by relative rotation of an adapter interdisposed between the stem and the head. In one example, a shoulder prosthesis comprises a stem having a first longitudinal axis. The shoulder prosthesis can also include an adaptor including a first taper. The first taper can have a first taper axis. The shoulder prosthesis can include a head rotatably supported by the adaptor. The head can have a semi-spherical articulating surface. The head can be coupled to the first taper and can be positionable relative to the stem through rotation of the adaptor about the first taper axis for adjusting an offset of the head relative to the longitudinal axis of the stem.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/120,111, filed on May 2, 2005, which is a divisional of U.S. patentapplication Ser. No. 10/192,787, filed on Jul. 10, 2002, now U.S. Pat.No. 6,942,699, issued Sep. 13, 2005. U.S. patent application Ser. No.10/192,787 claims the benefit of U.S. Provisional Application No.60/304,651, filed Jul. 11, 2001. The disclosures of the above referencedapplications are incorporated herein by reference.

BACKGROUND

The present teachings relate to a prosthesis for replacing andreconstructing a portion of the humerus and more specifically to amodular humeral prosthesis, which allows for total shoulder jointreplacement.

The shoulder joint is considered to be one of the most complex joints inthe body. The scapula, the clavicle and the humerus all meet at theshoulder joint. The head of the humerus fits into a shallow socket ofthe scapula called the glenoid fossa to form a mobile joint. When thejoint is articulated, the humeral head moves in the glenoid fossa toprovide a wide range of motion. The shoulder joint may suffer fromvarious maladies including rheumatoid arthritis, osteoarthritis, rotatorcuff arthropathy, a vascular necrosis, bone fracture or failure ofprevious joint implants. If severe joint damage occurs and no othermeans of treatment is found to be effective, then a total shoulderreconstruction may be necessary.

A shoulder joint prosthesis generally includes the replacement of theball of the humerus and, optionally, the socket of the shoulder bladewith specially designed artificial components. The bio-kinematics, andthus the range of motion in the shoulder vary greatly among prospectivepatients for reconstruction shoulder surgery. The humeral componenttypically has a metal shaft or stem with a body portion that is embeddedin the resected humerus and a generally hemispherical head portionsupported on the stem. The head slidingly engages a glenoid implant onthe glenoid fossa. During reconstructive surgery, the components of theprosthesis are matched with the bio-kinematics of the patient in aneffort to maintain the natural range of motion of a healthy shoulderjoint. Thus, a shoulder prosthesis design must be readily adaptable to awide range of bio-kinematics for prospective patients.

In this regard, shoulder prostheses are generally available as eitherunitary structures or modular components. With unitary shoulderprosthesis, a large inventory of differently sized prostheses must bemaintained to accommodate the different bone sizes and jointconfigurations of the prospective patients. With such unitary shoulderprosthesis, the patient is typically evaluated by x-ray to determine theapproximate prostheses size needed for reconstruction. A number ofdifferently sized prostheses are selected as possible candidates basedupon this preliminary evaluation. Final selection of the appropriatelysized prosthesis is made during the surgery. With unitary shoulderprosthesis, each design represents a compromise that is unable toachieve all of the natural range of motion of a healthy shoulder jointbecause of the fixed geometric configuration in their design.

Modular prostheses systems which reduce the need to maintain largeinventories of various sized components are well known in the art.Conventionally, the humeral prosthesis includes two components—a humeralstem component and a spherical head releasably coupled to the stem.Alternately, a three component design is known in which the stem andshoulder are interconnected with an adapter. In either of the two-pieceor three-piece designs, a radial offset or angulator inclination of thehead relative to the stem is provided in individual components. Forexample, in the three-piece design, an adapter may be configured with afixed radial offset of 2 millimeters or an angular inclination of 5degrees. Different radial offsets or angular inclinations are achievedthrough the use of different adapters or heads. In this regard,conventional modular shoulder prosthesis kits include multiple redundantcomponents such as adapters and heads to achieve a range of prostheticoptions. While providing an advantage over the unitary design inreducing the number of components needed, a rather large inventory ofhead components and/or adapter components must be maintained to providethe desired range of geometric configurations with the conventionalmodular shoulder prostheses. Therefore, there is a need for modularshoulder prostheses which are readily adaptable to provide a range ofgeometric configurations, i.e. radial offsets of angular inclinationwhile minimizing the number of components required.

SUMMARY

In accordance with the present teachings, a modular joint prosthesissystem is provided. Specifically, a humeral component for a totalshoulder prosthesis includes an adapter and a head component whichcooperate to provide a range of radial offsets and/or angularinclinations and which are adapted to be used in conjunction with astem.

In one embodiment, a humeral component for a total shoulder prosthesisis provided for adjustable radial offset of the head with respect to thestem. The shoulder prosthesis includes an adapter interposed between astem and a head. The adapter is eccentrically coupled to the stem suchthat relative angular positioning of the adapter on the stem will effecta first adjustment in the radial offset. Likewise, the head component iseccentrically coupled to the adapter as such that relative angularposition of the head on the adapter will effect a second radial offsetadjustment. By selectively positioning the adapter and the headcomponent with respect to the stem, an infinite adjustment of the radialoffset within a given range may be achieved. In one example, indicia areprovided at the interface between the adapter and the head to indicatethe offset vector (i.e., offset amount and direction).

In another embodiment, a humeral component for a total shoulderprosthesis is provided for adjustable angular inclination of the headcomponent relative to the stem component. The shoulder prosthesisincludes an adapter interposed between a stem and a head. The adapter iscoupled to the stem in a first angled or non-orthogonal orientation suchthat relative rotational positioning of the adapter on the stem willeffect a first adjustment in the direction of the angular inclination.Likewise, the adapter is coupled to the head in a second angled ornon-orthogonal orientation as such that relative rotational position ofthe head on the adapter will effect a second adjustment in the directionof the angular inclination. By selectively positioning the adapter andthe head component with respect to the stem, an infinite adjustment ofthe angular inclination within a given range may be achieved.

In yet another embodiment, the present teachings include an adapterinterposed between a stem and a head. The adapter includes a ball studhaving a shank coupled to the stem and a ring coupled to the head. Thering has a spherical bearing surface which cooperates with a ballportion of the ball stud such that an angular adjusted between the ballstud and the ring may be effected. The ring is eccentrically coupled tothe head such that relative angular positioning of the ring in the headwill effect an adjustment in the radial offset.

The joint prosthesis system of the present teachings provides greatflexibility in the adjustment of important bio-kinematic parameters forthe prosthesis systems while minimizing the number of componentsrequired for the modular system.

Also provided according to the present teachings is a shoulderprosthesis comprising a stem having a first longitudinal axis. Theshoulder prosthesis can also include an adaptor including a first taper.The first taper can have a first taper axis. The shoulder prosthesis canalso include a plurality of indicia. The shoulder prosthesis can includea head rotatably supported by the adaptor. The head can have asemi-spherical articulating surface. The head can be coupled to thefirst taper and can be positionable relative to the stem throughrotation of the adaptor about the first taper axis for adjusting aradial offset of the head relative to the longitudinal axis of the stem.The plurality of indicia can indicate an alignment of the radial offset.

Further provided is a shoulder prosthesis comprising a stem having alongitudinal axis and a proximal face. The proximal face can define abore. The shoulder prosthesis can include an adaptor having a firstportion coupled to a second portion. At least a portion of the firstportion can be received within the bore of the stem to couple theadaptor to the stem. The first portion can also have a first diameter.The second portion can have a second diameter different than the firstdiameter, and can define a first taper. The adaptor can also include aplurality of indicia. The shoulder prosthesis can include a head havinga bottom face opposite a semispherical articulating surface. The bottomface can have a second taper that mates with the first taper of thesecond portion to couple the head to the adaptor. The rotation of theadaptor relative to the stem can adjust the radial offset of the headrelative to the longitudinal axis of the stem. The plurality of indiciaon the adaptor can indicate an alignment of the radial offset.

According to the present teachings, provided is a shoulder prosthesiscomprising a stem having a longitudinal axis and a proximal face. Theproximal face can define a bore. The shoulder prosthesis can include anadaptor having a first portion opposite a second portion. At least aportion of the first portion can be received within the bore of the stemto couple the adaptor to the stem. The first portion can have a firstdiameter and can be positioned about a first axis. The second portioncan have a second diameter smaller than the first diameter. The secondportion can define a first taper and can be positioned about a secondaxis. The second axis can be offset from the first axis. The adaptor canalso include a plurality of indicia. The shoulder prosthesis can alsoinclude a head having a semispherical articulating surface and a bottomface opposite the semispherical articulating surface. The head can alsoinclude a third axis, which can be offset from the first axis and thesecond axis. The bottom face can have a second taper that mates with thefirst taper of the second portion to couple the head to the adaptor. Therotation of the adaptor relative to the stem can adjust the radialoffset of the head relative to the longitudinal axis of the stem. Theplurality of indicia on the adaptor can indicate an alignment of theradial offset.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present teachings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present teachings in any way.

FIG. 1 is an exploded front view of a modular shoulder prosthesis systemin accordance with the present teachings;

FIG. 2 is a normal view of the adapter and head components of the deviceillustrated in FIG. 1 shown in an assembled state;

FIG. 3 is an exploded front view of an alternate embodiment of themodular shoulder prosthesis system illustrated in FIG. 1;

FIG. 4 is a cross-sectional view of the adapter and head shown in FIG. 3arranged to provide a maximum radial offset;

FIG. 5 is a cross-sectional view of the adapter and head shown in FIG. 4and arranged to provide a minimum radial offset;

FIG. 6 is an exploded front view of a second alternative embodiment of amodular shoulder prosthesis system according to the present teachings;

FIG. 7 is a normal view of the adapter and head illustrated in FIG. 6shown in an assembled state;

FIG. 8 is an alternate embodiment of the modular shoulder prosthesissystem illustrated in FIG. 6;

FIG. 9 is a partial cross-sectional view showing the adapter and head ofFIG. 8 arranged to provide a maximum angular inclination;

FIG. 10 is an illustration of the adapter and head similar to that shownin FIG. 9 and arranged to provide a minimum angular inclination;

FIG. 11 is an exploded front view of a third alternative embodiment of amodular shoulder prosthesis system according to the present teachings;

FIG. 12 is a normal view of the adaptor and head components of thedevice shown in FIG. 11 oriented in a first position; and

FIG. 13 is a normal view similar to FIG. 12 with the components orientedin a second position.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present teachings, application, or uses. It shouldbe understood that throughout the drawings, corresponding referencenumerals indicate like or corresponding parts and features. Although thefollowing description is related generally to a modular joint prosthesissystem which provides adjustment of the radial offset and/or angularinclination of the head relative to the stem, it will be understood thatthe system as described and claimed herein can be used in anyappropriate surgical procedure. Thus, it will be understood that thefollowing discussions are not intended to limit the scope of the presentteachings and claims herein.

With reference now to FIG. 1, shoulder prosthesis 20 in accordance withthe present teachings is illustrated to include a stem 22, an adapter 24and a head 26. Stem 22 includes a rod portion 28 adapted to be receivedin the medullary canal of the humerus. A plurality of fins 30 are formednear the upper end of rod 28 for locating and fixing the stem within ahumerus. A male taper 32 extends obtusely from rod 28 to provide alocation for interconnecting stem 22 with adapter 24. Male taper 32extends from stem 22 along axis 34. Stem 22 is of the type manufacturedand sold by Biomet, Inc. as a component in its Bi-Angular® ShoulderSystem.

Adapter 24 is a generally cylindrical disc having a female taper 36formed therein for receiving male taper 32 of stem 22. The outer surface38 of adapter 24 defines a male taper. Female taper 36 is eccentricallylocated in adapter 24 such that central axis 34 of female taper 36 isnot collinear with central axis 40 of adapter 24. Instead, central axis40 is radially offset from central axis 34 by an amount indicated asr_(a).

Head 26 includes a semispherical surface 42 defined about central axis44. Bottom face 46 is formed opposite semispherical surface 42 and has afemale taper 48 formed therein which is configured to receive adapter 24along central axis 40. In this regard, female taper 48 is formedeccentrically within head 26 such that a radial offset r_(b) existsbetween central axis 40 and central axis 44.

As previously described, the eccentric relationship of central axes 34,40 and 44 provide an arrangement whereby a relative rotationalpositioning of adapter 24 with respect to head 26 adjusts the radialoffset within a given range. As best seen in FIG. 2, relativepositioning of adapter 24 within female taper 48 of head 26 causescentroid 50 defined by female taper 36 to trace a helical path 52relative to centroid 54 defined by central axis 40. Helical path 62terminates at centroid 56 defined by central axis 34. A maximum radialoffset is achieved when centroid 50 is located directly oppositecentroid 56. Similarly, a minimum offset is achieved when centroid 50aligns with centroid 56. In one example, the maximum radial offset is 10mm and the minimum radial offset is 0 mm. However, one skilled in theart will recognize that the range of offset may be modified based on thedesign criteria for a given modular prosthesis system.

With continuing reference to FIG. 2, the shoulder prosthesis 20 isprovided with indicia 64 facilitating adjustment and alignment of theradial offset. Specifically indicia 60 includes a first set ofindicators 62 formed on adapter 24 and a second set of indicators 64formed on bottom face 46 of head 26. First and second indicators 62, 64have a magnitude value associated therewith indicating the amount ofradial offset. Furthermore, head indicators 64 include an enlargedarrowhead which indicate the direction of the radial offset. In thismanner, indicia 60 provide a radial offset vector which may be utilizedto precisely align adapter 24 and head 26 and achieve the desired radialoffset.

For example, as shown in FIG. 2, adapter indictor 62.10 associated witha 10 millimeter offset is aligned with head indictor 64.10 associatedwith 0, 10 offset. Thus, the relative angular position of adapter 24with respect to head 26 shown in FIG. 2 provides a 10 millimeter offsetand the direction of the offset is indicated by arrowhead 64.10. Theradial offset may be reduced by removing adapter 24 from head 26,rotating adapter 24 until indicia 60 are properly aligned and insertingadapter 24 into female taper 48 of head 26. For example, an offset of 4millimeters would be obtained by aligning adapter indictor 62.4 withhead indictors 64.4 at which point a 4 millimeter offset in thedirection of arrowhead 64.4 would be achieved. In one example, athreaded through bore 66 may be formed in adapter 24 for receiving athreaded member to facilitate a disassembly of adapter 24 from head 26.In certain applications, a removeable plug (not shown) in the form of abio-compatible cement or the like may be disposed in bore 66 to minimizejoint fluid from entering the interface between the adapter 24 and thehead 26 through the bore 66.

With reference now to FIGS. 3 through 5, an alternate embodiment of thepresent teachings is illustrated in which the adapter has a first maletaper adapted to engage the stem and a second male taper adapted toengage the head. With reference now to FIG. 3, stem 22′ includes a rodportion 28′ and a female taper 32′ formed in the end opposite rod 28′which defines central axis 34′. Stem 22′ is of the type manufactured andsold by Biomet as a component of its Bio-Modular® Shoulder System.Adapter 24′ has a first male taper 36′ adapted to be inserted intofemale taper 32′ and a second male taper 38′ formed along central axis40′. Head 26′ includes a semispherical surface 42′ defined about centralaxis 44′. Bottom face 46′ has a female taper 48′ formed therein which isadapted to receive male taper 38′ of adapter 24′. Central axis 40′ isoffset from central axis 34′ as indicated at r_(a)′ and central axis 44′is offset from central axis 40′ as indicated at r_(b)′. As in the firstembodiment, relative rotational positioning of adapter 24′ and head 26′provides an adjustable radial offset for shoulder prosthesis 20′.

With reference now to FIG. 4, central axis 34′ of male taper 36′ islocated directly opposite central axis 44′ of head 26′ to provide amaximum radial offset. With reference now to FIG. 5, head 26′ has beenrotated 180 degrees relative to adapter 24′ such that central axis 44′is collinear with central axis 34′. In this orientation, a minimumradial offset is provided. Indicia similar to that described above withreference to FIG. 2 facilitates alignment of shoulder prosthesis 20′.

Based on the foregoing detailed description, one skilled in the art willreadily recognize that one aspect of the present teachings is directedto an adapter and head having eccentric configurations such that arelative rotation therebetween provides an adjustable range of offsetconfiguration.

With reference now to FIGS. 6 through 10, a second alternativeembodiment of the present teachings is illustrated which provides foradjustment of the angular inclination between the stem component and thehead component in a manner similar to that described with reference tothe radial offset. Specially, the shoulder prosthesis system 120 of thesecond alternative embodiment includes a stem 122, a head 124 having afirst angular orientation and an adapter 126 interconnecting the stem122 and the head 124 such that the adapter 126 has a second angularinclination. The adapter 124 is configured to be rotatably positionablewith respect to the head 126 such that the angular inclination of thehead 126 relative to the stem 122 may be adjusted.

With specific reference to FIG. 6, shoulder prosthesis 120 includes stem122 having rod 128 extending therefrom. A plurality of fins 130 areformed longitudinally along rod 128 parallel to central longitudinalaxis A near the upper end of stem 122. A male taper 132 extends from rod128 at an obtuse angle α with respect to the central longitudinal axis Aand defines a central axis 134.

Adapter 124 is a generally cylindrical disc having a female taper 136formed therein. The outer surface of adapter 124 defines a male taper138. The central axis 140 of adapter 124 is configured at a firstangular orientation with respect to central axis 134. Specifically,central axis 140 is defined by the angle at which female taper 130 isoriented relative to the bottom surface 125 of adapter 124. In oneexample, central axis 140 is disposed at a +5 degree angular inclinationwith respect to central axis 134.

Head 126 includes a semispherical surface 142 and a flat bottom face 146having a female taper 148 formed therein. Female taper 148 definescentral axis 144 which is disposed at an angular inclination relative toa central axis 140. Specifically, central axis 144 is defined by theangle at which female taper 144 is oriented relative to bottom face 146.In one example, central axis 144 is disposed at a −5 degree angularinclination with respect to central axis 140.

The relative rotational position of adapter 124 with respect to the head126 defines the adjustment to the prosthesis inclination relative tocentral axis 34. For example, as illustrated in FIG. 6, adapter 126provides a +5 degree inclination which is canceled by the −5 inclinationprovided in head 126. Thus, when adapter 124 and head 126 are assembleda net zero angular inclination is achieved. An angular adjustment may beprovided by rotating adapter 124 relative to head 126 such that a netangular inclination is provided. For example, when adapter 124 isrotated clockwise 90 degrees, the angular inclination of central axis140 combines with the angular inclination of central axis 144 to providea +5 degree angular inclination of head 126 relative to central axis134. Likewise, an additional 90 degree rotation of adapter 124 willprovide an overall adjustment of +10 degrees in the angular inclination.In one example, a range of angular inclination is provided between 0°and 10°. However, one skilled in the art will recognize that the rangeof angular inclination may be modified based on the design criteria fora given modular prosthesis system.

With continuing reference to FIG. 7, adapter 124 and head 126 areprovided with inclination indicia 160 which facilitates identificationof the magnitude and direction of the angular inclination provided byshoulder prosthesis system 120. Specifically, angular indicia 160includes a first indictor 162 on adapter 124 and a plurality of secondindicators 164 provided on bottom face 146 of head 126. Adapterindicator 162 is an arrowhead which indicates the direction of theangular inclination. Head indicators 164 provide a magnitude of angularinclination as well as an alignment mark which cooperates with adapterindictor 162 to provide the angular inclination vector (i.e. magnitudeand direction).

With reference now to FIGS. 8 through 10, an alternate embodiment to thesecond alternative embodiment is illustrated in which the adapter has afirst male taper adapted to engage the stem and a second male taperadapted to engage the head. With reference now to FIG. 8, stem 122′includes a rod portion 128′ and a female taper 132′ formed in the endopposite rod 128′ which defines central axis 134′. Adapter 124′ has afirst male taper 136′ adapted to be inserted into female taper 132′ anda second male taper 138′ formed along central axis 140′. Head 126′includes a semispherical surface 142′ defined about central axis 144′.Bottom face 146′ has a female taper 148′ formed therein which is adaptedto receive male taper 138′ of adapter 124′. Central axis 140′ isangularly inclined relative to central axis 34′ and central axis 144′ isangularly inclined relative to central axis 140′. Relative rotationalpositioning of adapter 124′ and head 126′ provides an adjustable angularinclination for shoulder prosthesis 120′.

With reference now to FIG. 9, the angular inclination of central axis134′ of male taper 136′ is complementary with the central axis 144′ ofhead 26′ to provide a maximum angular inclination. With reference now toFIG. 10, head 126′ has been rotated 180 degrees relative to adapter 124′such that the angular inclination of central axis 144′ is opposingcentral axis 134′ to provide a minimum angular inclination.

From the foregoing description of various embodiments, one skilled inthe art will readily recognize that the present teachings are directedto a modular shoulder prosthesis in which the radial offset and/or theangular inclination (i.e. inversion and retroversion) of the headrelative to the stem may be adjusted by relative rotational positioningof an adapter interdisposed between the stem and head components of theshoulder prosthesis. In this way, a range of radial offsets and/orangular inclinations may be provided without requiring numerousadditional components. The various embodiments have discussed a radialoffset adjustment or an angular inclination adjustment independently;however, one skilled in the art will readily recognize that a shoulderprosthesis system may incorporate both aspects of a radial and angularadjustment. Where a single adapter utilized to interconnect the stem andthe head, an interrelationship exists between the radially offsetadjustment and the angular inclination adjustment. In combination, asystem could be employed which utilized two intermediate adapters suchthat the radial offset and angular inclination adjustment are isolatedand thus independent. For example, the interface between a first adapterand a second adapter would provide the desired radial adjustment asdescribed in particular reference to the first embodiment and theinterface between the second adapter and the head would provide theangular inclination as described with reference to the secondalternative embodiment. In such a system, each of the radial offset andangular inclination adjustments would be provided by a single interface,thereby minimizing the interrelation between both adjustments resultingfrom a single intermediate adapter.

With reference now to FIGS. 11-13, a third alternative embodiment of thepresent teachings is illustrated which provides for adjustment of boththe radial offset and the angular inclination. Specifically, theshoulder prosthesis 210 is provided and includes a stem 212, an adaptor214 and a head 216. The stem 212 includes a longitudinal axis A alongits length and further includes a rod portion 218 adapted to be receivedinto the medullary canal of the humerus. A plurality of fins 220 areformed near the proximal end of the rod 218 for locating and fixing thestem 212 within the humerus whereby the proximal end of the rod 218 hasa substantially larger body than that of the distal end and includes aproximal face 222 having a bore 224 formed therein along a central axis226 for receiving the adaptor 214. The proximal face 222 extends fromthe stem 212 along axis 226 and provides a location for interconnectingthe stem 212 with the adaptor 214. Further, the proximal face 222provides sufficient clearance for angular and radial adjustments of theadaptor 214 and the head 216 as will be discussed in more detail below.

The adaptor 214 is a generally cylindrical member including an outerring 228 having a central axis 230 and a ball stud 232 rotatablyconnected to the ring 228. The ring 228 includes an attachment aperture234 having a central axis 236 formed therethrough for rotatableengagement with the ball stud 232. The ring 228 further includes anouter surface having a male taper 238 for engagement with the head 216.

The ball stud 232 includes a shank segment 233 for engagement with thebore 224 of the stem 212 and a divided ball segment 240 for attachmentto attachment aperture 234 of the ring 228. The ball stud 232 furtherincludes a second bore 242 formed therein for interaction with afastener 244 for selectively securing the ring 228 to the ball stud 232in a fixed orientation. Fastener 244 includes a wedge portion 254 and aset screw 256 as best shown in FIG. 11. Set screw 256 is received by acentral bore of the wedge 254, whereby as the set screw 256 is driveninto the wedge 254, the wedge 254 expands within the attachment aperture234 of the ring 228 thereby securing the ring 228 and ball stud 232 in afixed relationship. In this regard, the central axis 236 of the ballstud 232 is concentric with central axis 226 of the proximal face 222and is received by the attachment aperture 234 such that the centralaxis 236 of the ball stud 232 is eccentric to the central axis 230 ofthe ring 228 as indicated by r_(a).

The head 216 is rotatably supported by the adaptor 214 and includes asemispherical surface 246 defined about a central axis 248 adapted formating engagement with the glenoid cavity of a scapula. The head 216further includes a bottom surface 250 formed opposite the semisphericalsurface 246 having a female taper 252 for mating engagement with themale taper 238 of the ring 228. In this regard, the female taper 252 isreceived eccentrically within the head 216 such that a radial offsetr_(b) exists between the central axis 230 of the ring 228 and thecentral axis 248 of the head 216. While the present teachings disclose ahead 216 for mating engagement with the glenoid cavity of a scapula, itis anticipated that the head 216 could also be received by a prostheticdevice replacing a severely damaged glenoid cavity and should beconsidered within the scope of the present teachings.

As previously described, the eccentric relationship of the central axes230, 236 and 248 provides an arrangement whereby a relative rotationalpositioning of the adaptor 214 with respect to the head 216 or arelative rotational positioning of the adaptor 214 with respect to theball stud 232 or a combination thereof adjusts the radial offset of thehead 216 relative to the longitudinal axis A of the stem 212.

With particular reference to FIG. 13, relative positioning of the head216 to the longitudinal axis A of the stem 212 is accomplished by afirst radial adjustment method. In the first radial adjustment method,the relative positioning of the ring 228 within the female taper 252 ofthe head 216 causes the central axis 248 of the head 216 to be rotatedrelative to the central axis 230 of the ring 228. The radial offsetbetween the central axis 248 and the central axis 230 is again denotedby r_(b) at its minimum and by r_(b)′ at its maximum value. FIG. 2further traces the movement of axis 248 from r_(b) to r_(b)′ asindicated by path 249, while each position along path 249 signifies apotential adjustment of the head 216 relative to the longitudinal axis Aof the stem 212.

With particular reference to FIGS. 12 and 13, relative positioning ofthe head 216 to the longitudinal axis A of the stem 212 is accomplishedby a second radial adjustment method. In the second radial adjustmentmethod, the relative positioning of the central axis 230 of the ring 228and the central axis 236 of the ball stud 232 causes the central axis248 of the head 216 to be rotated. Again, r_(a) is used to designate theminimum offset between the central axis 230 of the ring 228 and thecentral axis 236 of the ball stud 232 while r_(a)′ is used to designatethe maximum offset. FIG. 3 further traces the movement of axis 248 fromr_(a) to r_(a)′ as indicated by path 251, while each position along path251 signifies a potential adjustment of the head 216 relative to thelongitudinal axis A of the stem 212. For discussion purposes, the head216 does not rotate relative to the ring 228 when making an adjustmentof the ball stud 232 relative to the ring 228, but it should beunderstood that both adjustment methods could be used concurrently toachieve an overall desired radial offset of the head 216 relative to thelongitudinal axis A of the stem 212.

In addition to providing a radial offset, the shoulder prosthesis 210further provides an angular adjustment of the head 216 relative to thelongitudinal axis A of the stem 212 for both inversion and retroversionadjustments. As best shown in FIG. 3, the central axis 248 of the head216 rotates about the central axis 236 of the ball stud 232, which isconcentric with the central axis 226 of the first bore 224. Aspreviously discussed, the divided ball segment 240 of the ball stud 232rotatably supports the ring 228 while the ring 228 supports the head216. By articulating either the head 216 or the ring 228, the ring 228will rotate on the divided ball segment 240 of the ball stud 232,thereby providing the head 216 with an angular adjustment relative tothe longitudinal axis A of the stem 212. For discussion purposes, thefirst and second radial adjustment methods are not utilized while makingan angular adjustment of the head 216, however, it should be understoodthat both adjustment methods may be used concurrently with the angularadjustment method and with one another to achieve an overall desiredangular and radial relationship of the head 216 relative to thelongitudinal axis A of the stem 212.

With continuing reference to FIGS. 2 and 3, the shoulder prosthesis isprovided with indicia 260 facilitating adjustment and alignment of theradial offset. Specifically, indicia 260 includes a first set ofindicators 262 formed on the ring 228 and a second set of indicators 264formed on the bottom face 250 of the head 216. First and secondindicators 262, 264 have a magnitude value associated therewithindicating the amount of radial offset. Furthermore, the head indicators264 include an enlarged arrowhead which indicates the direction of theradial offset. In this manner, indicia 260 provide a radial offsetvector which may be utilized to precisely align the adaptor 214 and thehead 216 and achieve the desired radial offset.

In reference to all of the above-described embodiments, various taperedsurfaces have been referenced at interfaces between the stem, adapterand head. In one example, these tapered surfaces are configured asmorse-type tapers which provide a self locking interface. Whilemorse-type tapers are described herein, one skilled in the art willreadily recognize that other means may be incorporated for providing alocking interface between the various components of the shoulderprosthesis system. In this regard, one or more interfaces may beinterlocked with the use of an additional fastener to insure lockingengagement therebetween.

While specific examples have been described in the specification andillustrated in the drawings, it will be understood by those of ordinaryskill in the art that various changes can be made and equivalents can besubstituted for elements thereof without departing from the scope of thepresent teachings. Furthermore, the mixing and matching of features,elements and/or functions between various examples is expresslycontemplated herein so that one of ordinary skill in the art wouldappreciate from the present teachings that features, elements and/orfunctions of one example can be incorporated into another example asappropriate, unless described otherwise, above. Moreover, manymodifications can be made to adapt a particular situation or material tothe present teachings without departing from the essential scopethereof. Therefore, it is intended that the present teachings not belimited to the particular examples illustrated by the drawings anddescribed in the specification, but that the scope of the presentteachings will include any embodiments falling within the foregoingdescription.

1. A shoulder prosthesis comprising: a stem having a first longitudinalaxis; an adaptor including a first taper, the first taper having a firsttaper axis; a plurality of indicia associated with the adaptor; and ahead rotatably supported by the adaptor, the head having asemi-spherical articulating surface, wherein the head is coupled to thefirst taper and is positionable relative to the stem through rotation ofthe adaptor about the first taper axis for adjusting a radial offset ofthe head relative to the longitudinal axis of the stem and the pluralityof indicia indicate an alignment of the radial offset.
 2. The shoulderprosthesis of claim 1, wherein the first taper further comprises a firstmale taper and the adaptor further comprises a second portion.
 3. Theshoulder prosthesis of claim 2, wherein the second portion has a secondaxis and the second axis is offset from the first taper axis.
 4. Theshoulder prosthesis of claim 1, wherein the semi-spherical articulatingsurface is a generally hemispherical outer surface adapted for matingengagement with a glenoid cavity of a scapula and a bottom surface ofthe head defines a female taper formed therein.
 5. The shoulderprosthesis of claim 4, wherein the female taper rotatably receives thefirst taper of the adaptor.
 6. The shoulder prosthesis of claim 1,wherein the stem further comprises a shank segment extending therefromalong a second longitudinal axis, and the shank segment rotatablyreceives the adaptor.
 7. The shoulder prosthesis of claim 1, wherein thehead axis is angularly inclined relative to the first tapered axis. 8.The shoulder prosthesis of claim 1, wherein the stem further comprises aproximal face having a bore, and the adapter further comprises: a firstportion that includes the first taper and has a first diameter; and asecond portion that extends from the first portion, the second portionhaving a second diameter smaller than the first diameter, wherein atleast a portion of the second portion is receivable within the bore ofthe proximal face to enable the rotation of the adaptor about the firsttaper axis.
 9. A shoulder prosthesis comprising: a stem having alongitudinal axis and a proximal face, the proximal face defining abore; an adaptor having a first portion coupled to a second portion, atleast a portion of the first portion received within the bore of thestem to couple the adaptor to the stem, the first portion having a firstdiameter, the second portion having a second diameter different than thefirst diameter and the second portion defining a first taper, theadaptor including a plurality of indicia; and a head having a bottomface opposite a semispherical articulating surface, the bottom facehaving a second taper that mates with the first taper of the secondportion to couple the head to the adaptor, wherein the rotation of theadaptor relative to the stem adjusts the radial offset of the headrelative to the longitudinal axis of the stem and the plurality ofindicia on the adaptor indicate an alignment of the radial offset. 10.The shoulder prosthesis of claim 9, wherein the second diameter issmaller than the first diameter.
 11. The shoulder prosthesis of claim10, wherein the adaptor further comprises a one-piece adaptor.
 12. Theshoulder prosthesis of claim 10, wherein the first portion and thesecond portion cooperate to define an aperture for receipt of afastener.
 13. The shoulder prosthesis of claim 12, wherein the fasteneris operable to fix the adaptor in a desired radial offset.
 14. Theshoulder prosthesis of claim 13, wherein the second portion furthercomprises a ring having an attachment aperature and the first portionfurther comprises a ball stud having a divided ball segment and a secondbore, and the fastener is received through a portion of the attachmentaperture and a portion of the second bore.
 15. The shoulder prosthesisof claim 14, wherein the ring rotates about the divided ball segment onthe ball stud.
 16. A shoulder prosthesis comprising: a stem having alongitudinal axis and a proximal face, the proximal face defining abore; an adaptor having a first portion opposite a second portion, atleast a portion of the first portion received within the bore of thestem to couple the adaptor to the stem, the first portion having a firstdiameter and positioned about a first axis, the second portion having asecond diameter different than the first diameter, the second portiondefining a first taper and positioned about a second axis, the secondaxis offset from the first axis, the adaptor including a plurality ofindicia; and a head having a semispherical articulating surface and abottom face opposite the semispherical articulating surface, the headhaving a third axis offset from the first axis and the second axis, thebottom face having a second taper that mates with the first taper of thesecond portion to couple the head to the adaptor, wherein the rotationof the adaptor relative to the stem adjusts the radial offset of thehead relative to the longitudinal axis of the stem and the plurality ofindicia on the adaptor indicate an alignment of the radial offset. 17.The shoulder prosthesis of claim 16, wherein the adaptor furthercomprises a one-piece adaptor.
 18. The shoulder prosthesis of claim 16,wherein the first taper is a male taper and the second taper is a femaletaper.
 19. The shoulder prosthesis of claim 16, wherein the rotation ofthe adaptor further adjusts an angular inclination of the head relativeto the stem.
 20. The shoulder prosthesis of claim 16, wherein the firstportion and the second portion cooperate to define an aperture forreceipt of a fastener.